1. Field of the Invention
The present invention relates to a method of manufacturing an insulation coil for use in an electric rotating machine, in particular, a method of manufacturing an insulation coil excellent in the insulating properties and the thermal conduction.
2. Description of the Related Art
In a high output electric rotating machine, it is necessary, in order to efficiently dissipate generated heat, to improve the thermal conductivity of an insulation coil. So far, it has been tried to use high thermal conduction insulating material in an electrically insulating coating of an insulation coil.
As a coil insulated with a high thermal conduction insulating material, there is a coil insulated with an insulating material that includes mica flake layers solidly fixed to glass fabric; and a resin layer that is disposed in a space between the mica flake layers and contains inorganic particles such as boron nitride, aluminum nitride, silicon nitride, aluminum oxide, magnesium oxide, beryllium oxide and silicon carbide that have the thermal conductivity of 5 W/mK or more, wherein at least 90% by weight of the inorganic particles is particles having a particle diameter in the range of 0.1 to 15 μm.
The coil insulated with an insulating layer that contains inorganic particles having high thermal conductivity in a resin layer disposed in a space between the mica flake layers is manufactured according to the respective methods below.
According to a first method, an insulation tape made of a mica flake layer fixed to glass fabric is wound around a coil conductor, and in the wound insulation tape a liquid resin containing inorganic particles having high thermal conductivity is impregnated.
Furthermore, according to a second method, an insulation tape that is made of a mica flake layer fixed to glass fabric and is not yet wound around a coil conductor is impregnated with a liquid resin containing inorganic particles having high thermal conductivity, the insulation tape impregnated with the resin is wound around a coil conductor.
Still furthermore, according to a third method, an insulation tape that is made of a mica flake layer fixed to glass fabric and not yet wound around a coil conductor is impregnated with a liquid resin, on a surface of the resin-impregnated insulation tape inorganic particles having high thermal conductivity are coated, and the inorganic particle-coated insulation tape is wound around a coil conductor (for instance, JP-A-63-110929).
Furthermore, according to a fourth method, on an insulation tape that is made of a mica flake layer fixed to glass fabric and not yet wound around a coil conductor, a liquid resin containing inorganic particles having high thermal conductivity is coated, and the inorganic particle containing resin-coated insulation tape is wound around a coil conductor (for instance, JP-A-11-206056).
The reason for the high thermal conduction insulation coil having the high thermal conduction is because in a space between mica flake layers fixed to glass fabric in an insulating layer, not only the glass fiber and the resin that are small in the thermal conductivity, but also inorganic particles having high thermal conductivity are present.
According to the first method of manufacturing an insulation coil, in order to allow sufficiently containing inorganic particles between the mica flake layers of the insulating layer, the inorganic particle-containing resin is necessary to be easily penetrated between the wound insulation tapes; accordingly, the insulation tape made of a mica flake layer is necessarily wound loose. Accordingly, according to the method of manufacturing an insulation coil, there are problems in that the insulation tape is wound around the coil conductor with difficulty, and a thickness of the insulating layer becomes uneven and thicker.
Furthermore, according to the second through fourth methods of manufacturing an insulation coil, there are problems in that the inorganic particle layer is formed thicker on the insulation tape, the inorganic particle layer between the mica flake layers becomes thicker, resulting in the insulating layer itself becoming thicker.
The voltage endurance characteristics of an insulation coil depends on a number of layers of mica layer in an insulating layer, that is, the larger the number of layers is, the more excellent the voltage endurance characteristics become. However, since the insulation coil is inserted in a slot groove of a stator of an electric rotating machine, a thickness of the insulating layer of the insulation coil is restricted. Accordingly, according to existing methods of manufacturing an insulation coil, there are problems in that the insulation tape becomes thicker, the number of layers of mica layer in the insulating layer becomes smaller, and deterioration of the voltage endurance characteristics results.